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International Conference on Parallel and Distributed systems (ICPADS)

作者： Yanmin Zhu Lubin Liu Juan Li Jiadi Yu Chengnian Long Shanghai Key Lab of Scalable Computing and Systems Department of Computer Science and Engineering Shanghai Jiao Tong University Department of Automation Shanghai Jiao Tong University

ISBN: (纸本)9781467386692

Wireless local area networks (WLANs) are pervasive but crowded nowadays. It is of great importance for access points (APs) to adapt to the changing traffic conditions. Exiting approaches for channel selection largely rely on local channel assessment and adopt greedy selection strategies. They suffer a major limitation that an AP fail to take various traffic demands of clients into account. We have witnessed that wireless sensor networks are increasingly deployed everywhere. A ZigBee sensor operates on the 2.4G radio spectrum which overlaps the spectrum used by most WiFi APs. As a result, a ZigBee sensor is able to sense the traffic of different AP channels. Motivated by this important observation, we present the design, implementation and evaluation of OutSence, a system that enables APs to takes traffic volumes of clients into account. It makes use of channel utilization sensed by ZigBee sensors and allows an AP to select a channel of good performance. The salient feature of OutSence is that it exploits in-situ ZigBee sensors for APs to quickly adapt to short-term traffic variations (e.g., order of minutes). We have fully implemented OutSence on Telos B sensor nodes and off-the-self APs. Extensive experiments have been conducted and conclusive results demonstrate that OutSence effectively improves overall WLAN performance.

关键词： IEEE 802.11 Standard Zigbee Sensors Interference Computer architecture Channel allocation Microprocessors

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DEEL: Detecting elevation of urban roads with smartphones on wheels

DEEL: Detecting elevation of urban roads with smartphones on...

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IEEE Communications Society Conference on Sensor and Ad Hoc Communications and Networks (SECON)

作者： Yaoming Gong Yanmin Zhu Jiadi Yu Shanghai Jiao Tong University Shanghai CN Shanghai Key Lab of Scalable Computing and Systems Shanghai China Department of Computer Science and Engineering Shanghai Jiao Tong University Shanghai China

Elevated roads are built worldwide to alleviate urban traffic congestions. An elevated road may overlap with the ground surface road. This poses a great challenge to auto navigation systems. It is particularly difficult for auto navigation systems to determine if an vehicle is running on an elevated road because altitude readings from GPS (Global Positioning systems) receivers are of low accuracy. Without correct positioning of elevated or surface roads, an auto navigation system may recommend wrong routes which may lead to serious traffic accidents or cause drivers' anxiety. In this paper, we design a smartphone-based system called DEEL for detecting road elevation as the vehicle moves on urban roads. HMM-based models are built to characterize the patterns of vehicle dynamics with respect to the elevation of the road that the vehicle is moving on. The system leverages smartphone sensors to sense the instantaneous vehicle dynamics, including the 3D acceleration, the speed, and the number of perceived GPS satellites. Based on the sensed dynamics, it determines whether the vehicle is running on an elevated road or not in an online fashion. We have successfully implemented our system in Android-based smartphones. Extensive experiments demonstrate the system achieves a high accuracy of 92.1% with strong robustness to variations of vehicles, drivers and roads.

关键词： Roads Vehicles Smart phones Acceleration Gravity Global Positioning System Sensors

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Delay-constrained data aggregation in VANETs

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IEEE Transactions on Vehicular Technology 2015年第5期64卷 2097-2107页

作者： Zhu, Yanmin Zhao, Qingwen Zhang, Qian Department of Computer Science and Engineering Shanghai Jiao Tong University Shanghai200240 China Shanghai Key Lab of Scalable Computing and Systems Shanghai Jiao Tong University Shanghai200240 China Department of Computer Science and Engineering Hong Kong University of Science and Technology Kowloon Hong Kong

Data aggregation has been recognized as an effective technique for reducing communication costs while obtaining useful aggregated information. In this paper, we study the crucial problem of delay-constrained data aggregation in vehicular ad hoc networks (VANETs), which has not been well studied in the literature. With the analysis based on real traces, we observe that there is heterogeneity with node contact patterns, which indicates that some nodes contact other nodes more frequently. Motivated by this observation, we propose an approach called aTree. The centralized aTree first constructs a data aggregation tree based on the shortest path tree and then assigns a waiting time budget to each node on the tree based on dynamic programming. We further develop a distributed aTree, in which a shortest path tree is built in a distributed fashion, and nodes determine their waiting time budgets collab.ratively. We have performed extensive simulations on real taxi traces, and results show that our aTree schemes incur much lower transmission overhead while achieving the same performance compared with other schemes. © 1967-2012 IEEE.

关键词： Dynamic programming

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A distributed spectrum sharing algorithm in cognitive radio networks 20

A distributed spectrum sharing algorithm in cognitive radio ...

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20th IEEE International Conference on Parallel and Distributed systems, ICPADS 2014

作者： Sun, Wei Yu, Jiadi Liu, Tong Department of Computer Science and Engineering Shanghai Jiao Tong University China Shanghai Key Lab of Scalable Computing and Systems China

ISBN: (纸本)9781479976157

In this paper we study a social welfare maximization problem for spectrum sharing in cognitive radio networks. To fully use the spectrum resource, the spectrum owned by the licensed primary user (PU) can be leased to secondary users (SUs) for transmitting data. We first formulate the social welfare of a cognitive radio network, considering the cost for the primary user sharing spectrum and the utility gained for secondary users transmitting data. The social welfare maximization is a convex optimization, which can be solved by standard methods in a centralized manner. However, the utility function of each secondary user always contains the private information, which leads to the centralized methods disabled. To overcome this challenge, we propose an iterative distributed algorithm based on a pricing-based decomposition framework. It is theoretically proved that our proposed algorithm converges to the optimal solution. Numerical simulation results are presented to show that our proposed algorithm achieves optimal social welfare and fast convergence speed. © 2014 IEEE.

关键词： Convex optimization

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Mining large-scale GPS streams for connectivity refinement of road maps

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Computer Journal 2014年第9期58卷 2109-2119页

作者： Zhu, Yanmin Wang, Yin Forman, George Wei, Hong Shanghai Key Lab of Scalable Computing and Systems Shanghai China Department of Computer Science and Engineering Shanghai Jiao Tong University Shanghai China Facebook Menlo Park United States HP Labs Palo Alto United States

As people increasingly rely on road maps in the digital age, manually maintained maps cannot keep up with the demand for accuracy and freshness, evidenced by the recent iOS map incident and the bidding war for Waze. There are many research works on automatic map inference using GPS data, and some have suggested that Google and Waze automate their map update processes to some degree with user data. However, existing published work focuses on refining road geometry. In reality, connectivity issues at intersections, including missing connections and unmarked turn restrictions, are much more prevalent and also more difficult to infer. In this paper, we report our study on the connectivity issues in the OSM shanghai map using 21 months of GPS data from over $10\,000$ taxis. We first adapt a robust map matching algorithm. Then, we propose simple algorithms for detecting missing intersections, turn restrictions and road closures. Empirical results show that our algorithms of connectivity refinement for road maps are effective. © 2015 The British Computer Society. All rights reserved.

关键词： Global positioning system

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Energy-efficient identification in large-scale RFID systems with handheld reader

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IEEE Transactions on Parallel and Distributed systems 2014年第5期25卷 1211-1222页

作者： Zhu, Yanmin Jiang, Wenchao Zhang, Qian Guan, Haibing Department of Computer Science and Engineering Shanghai Jiao Tong University Shanghai Key Lab of Scalable Computing and Systems China Department of Computer Science and Engineering Hong Kong University of Science and Technology Hong Kong

Efficient identification of tags has been an essential operation for Radio Frequency IDentification (RFID) systems. In this paper, we consider the crucial problem of collecting all tags in a large-scale system through a handheld RFID reader. The reader has to move around due to the limited communication range of tags. We focus on the minimization of power consumption of the reader given the constraint on its movement distance. Two challenges must be addressed. First, the communication range of a tag is dependent on the reader. There is an intrinsic tradeoff between power saving and movement distance. Second, the number of sites at which the reader can collect tags can be numerous and the problem complexity is extremely high. We theoretically prove that the problem of minimizing the energy consumption of the reader is NP Complete (NPC). To solve the problem, we first analytically reveal that the time needed for reading a given number of tags is linearly proportional to the number of tags only. With this insight, we next propose an approach called ePath by constructing an energy-efficient candidate path and then incrementally pruning the path when the tag locations are given. We further relax the assumption on tag locations by extending ePath to exploit the tag distribution density knowledge only. Extensive simulations have been performed, and results show that our approach significantly reduces the power consumption of the reader comparing to an existing approach. © 1990-2012 IEEE.

关键词： Energy efficiency

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On deploying relays for connected indoor sensor networks

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Journal of Communications and Networks 2014年第3期16卷 335-343页

作者： Zhu, Yanmin Xue, Cuiyao Cai, Haibin Yu, Jiadi Ni, Lei Li, Minglu Li, Bo Shanghai Key Lab. of Scalable Computing and Systems Department of Computer Science and Engineering Shanghai Jiao Tong University China Department of Computer Science and Engineering Shanghai Jiao Tong University China Software Engineering Institute East China Normal University China Shanghai Jiao Tong University Hong Kong University of Science and Technology Hong Kong

This paper considers the crucial problem of deploying wireless relays for achieving a connected wireless sensor network in indoor environments, an important aspect related to the management of the sensor network. Several algorithms have been proposed for ensuring full sensing coverage and network connectivity. These algorithms are not applicable to indoor environments because of the complexity of indoor environments, in which a radio signal can be dramatically degraded by obstacles such as walls. We first prove theoretically that the indoor relay placement problem is NP-hard. We then predict the radio coverage of a given relay deployment in indoor environments. We consider two practical scenarios;wire-connected relays and radio-connected relays. For the network with wire-connected relays, we propose an efficient greedy algorithm to compute the deployment locations of relays for achieving the required coverage percentage. This algorithm is proved to provide a Hn factor approximation to the theoretical optimum, where Hn = 1 +1/2+⋯+1/n= ln(n) +1, and n is the number of all grid points. In the network with radio-connected relays, relays have to be connected in an ad hoc mode. We then propose an algorithm based on the previous algorithm for ensuring the connectivity of relays. Experimental results demonstrate that the proposed algorithms achieve better performance than baseline algorithms. © 2014 KICS.

关键词： Approximation algorithms

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Social welfare maximization in participatory smartphone sensing

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Computer Networks 2014年 73卷 195-209页

作者： Tong Liu Yanmin Zhu Department of Computer Science and Engineering Shanghai Jiao Tong University China Shanghai Key Lab of Scalable Computing and Systems China

Participatory smartphone sensing has lately become more and more popular as a new paradigm for performing large-scale sensing, in which each smartphone contributes its sensed data for a collab.rative sensing application. Most existing studies consider that smartphone users are strictly strategic and completely rational, which try to maximize their own payoffs. A number of incentive mechanisms are designed to encourage smartphone users to participate, which can achieve only suboptimal system performance. However, few existing studies can maximize a system-wide objective which takes both the platform and smartphone users into account. This paper focuses on the crucial problem of maximizing the system-wide performance or social welfare for a participatory smartphone sensing system. There are two great challenges. First , the social welfare maximization cannot be realized on the platform side because the cost of each user is private and unknown to the platform in reality. Second , the participatory sensing system is a large-scale real-time system due to the huge number of smartphone users who are geo-distributed in the whole world. A price-based decomposition framework is proposed in our previous work (Liu and Zhu, 2013), in which the platform provides a unit price for the sensing time spent by each user and the users return the sensing time via maximizing the monetary reward. This pricing framework is an effective incentive mechanism as users are motivated to participate for monetary rewards from the platform. In this paper, we propose two distributed solutions, which protect users’ privacy and achieve optimal social welfare. The first solution is designed based on the Lagrangian dual decomposition. A poplar iterative gradient algorithm is used to converge to the optimal value. Moreover, this distributed method is interpreted by our pricing framework. In the second solution, we first equivalently convert the original problem to an optimal pricing problem. Then, a distr

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Geographic routing based on predictive locations in vehicular ad hoc networks

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EURASIP Journal on Wireless Communications and Networking 2014年第1期2014卷 1-9页

作者： Yanmin Zhu Ruobing Jiang Jiadi Yu Zhi Li Minglu Li Department of Computer Science and Engineering Shanghai Jiao Tong University Shanghai China Shanghai Key Lab of Scalable Computing and Systems Shanghai China

Many geographic routing algorithms have been proposed for vehicular ad hoc networks (VANETs), which have the strength of not maintaining any routing structures. However, most of which rely on the availab.lity of accurate real-time location information. It is well known that vehicles can be intermittently connected with other vehicles. Thus, in such networks, it is difficult or may incur considerable cost to retrieve accurate locations of moving vehicles. Furthermore, the location information of a moving vehicle availab.e to other vehicles is usually time-lagged since it is constantly moving over time. Fortunately, we observe that the short-term future locations of vehicles can be predicted. Based on the important observation, we propose a novel approach for geographic routing which exploits the predictive locations of vehicles. Thus, we have developed a prediction technique based on the current speed and heading direction of a vehicle. As a result, the request frequency of location updates can be reduced. In addition, we propose two forwarding strategies and three buffer management strategies. We have performed extensive simulations based on real vehicular GPS traces collected from around 4,000 taxis in shanghai, China. Simulation results clearly show that geographic routing based on predictive locations is viable and can significantly reduce the cost of location updates.

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New words identification based on ensemble methods

New words identification based on ensemble methods

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2nd International Conference on Precision Mechanical Instruments and Measurement Technology, ICPMIMT 2014

作者： Zhang, Chen Chen, Yu-Quan Department of Computer Science and Engineer Shanghai Jiao Tong University Shanghai China MOE-Microsoft Key Lab. for Intelligent Computing and Intelligent Systems Shanghai Jiao Tong University Shanghai China

ISBN: (纸本)9783038351948

In order to identify new words in huge Chinese corpus efficiently, this paper comes up with an algorithm based on ensemble methods. At first we perform Chinese word segmenting with Trie and build segment-tree. Then we select words pattern drawing method, frequency filtering, independent word probability and naive Bayes model to be sub-models of ensemble methods and train them independently. At last we integrate results from different sub-models with a multi-layer model. In experiment, this algorithm is proved to be quite fast as well as product precise and high-coverage results. © (2014) Trans Tech Publications, Switzerland.

关键词： Bayesian networks

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